Selective aerobic oxidation of dimethylbiphenyls

Abstract

A process for selective oxidation of dimethyl-1,1′-biphenyl(s) to form methyl-1,1′-biphenyl mono-carboxylic acid(s), which can be esterified to form plasticizers, comprising contacting a solution of dimethyl-1,1′-biphenyl(s) in acetic acid in the presence of an oxidation catalyst and air under time and temperature conditions sufficient to oxidize the dimethyl-1,1′-biphenyl(s) into one or more methyl-1,1′-biphenyl mono-carboxylic acid(s) products, conducting at least one of (i) adding an antisolvent, or (ii) optimizing a total conversion of dimethyl-1,1′-biphenyl(s) by oxidation based upon a molar ratio of dimethyl-1,1′-biphenyl isomers, or (iii) precipitating the methyl-1,1′-biphenyl mono-carboxylic acid(s) products by lowering the temperature, or (iv) decreasing the oxidation reaction temperature to enhance conversion of aldehydes over methyl functional groups, so as to limit over-oxidation of the dimethyl-1,1′-biphenyl(s), wherein the oxidation reaction is conducted in the absence of bromide-containing catalysts.

The invention claimed is: 
     
       1. A process for selective oxidation of dimethyl-1,1′-biphenyl(s) to form methyl-1,1′-biphenyl mono-carboxylic acid(s), comprising:
 providing a mixture of dimethylbiphenyl isomers; 
 separating 2,3′- and 2,4′-isomers of dimethylbiphenyl in the mixture from 3,3′-, 3,4′-, and 4,4′-isomers of dimethylbiphenyl by distillation, and then dissolving the 3,3′-, 3,4′- and 4,4′-isomers of dimethylbiphenyl in acetic acid to form a solution; 
 contacting the solution with an oxidation catalyst and air under time and temperature conditions sufficient to oxidize the dimethyl-1,1′-biphenyl(s) into one or more methyl-1,1′-biphenyl mono-carboxylic acid(s) products; 
 conducting at least one of: 
 (i) adding an antisolvent, or 
 (ii) optimizing a total conversion of dimethyl-1,1′-biphenyl(s) by oxidation based upon a molar ratio of dimethyl-1,1′-biphenyl isomers, or 
 (iii) precipitating the methyl-1,1′-biphenyl mono-carboxylic acid(s) products by lowering the temperature, or 
 (iv) decreasing the oxidation reaction temperature to enhance conversion of aldehydes over methyl functional groups, 
 
       so as to limit over-oxidation of the dimethyl-1,1′-biphenyl(s),
 wherein the oxidation reaction is conducted in the absence of bromide-containing catalysts, and 
 wherein the total conversion is limited to 55-70% when the 3,3′-isomers of dimethylbiphenyl comprise less than 10 wt % of the solution, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates. 
 
     
     
       2. The process of  claim 1 , wherein the catalyst is Mn(II) acetate or Co(II) acetate or combinations of Co(II) acetate and other metal acetate catalysts. 
     
     
       3. The process of  claim 1 , comprising adding water as the antisolvent. 
     
     
       4. The process of  claim 1 , further comprising limiting the total conversion to 45-55% when the 3,3′-isomers of dimethylbiphenyl comprise between 10 and 30 wt % in the feed, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates. 
     
     
       5. The process of  claim 1 , further comprising limiting the total conversion to 30-45% when the 3,3′-isomers of dimethylbiphenyl comprise between 30 and 80 wt % in the feed, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates. 
     
     
       6. The process of  claim 1 , wherein precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products is achieved by removing solvent. 
     
     
       7. The process of  claim 1 , wherein precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products is achieved by optimizing the oxidation reaction temperature and solute concentrations of the methyl-1,1′-biphenyl mono-carboxylic acid(s), to cause precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products prior to over-oxidation. 
     
     
       8. The process of  claim 7 , wherein the oxidation reaction temperature is reduced from an oxidation initiation temperature to from about 40° C. to less than about 60° C. 
     
     
       9. The process of  claim 7 , wherein the solute concentration of methyl-1,1′-biphenyl mono-carboxylic acid(s) products is above about 2 wt %. 
     
     
       10. The process of  claim 1 , wherein the oxidation reaction temperature is controlled to be from about 100° C. to about 150° C. 
     
     
       11. The process of  claim 10 , wherein the oxidation reaction temperature is controlled to be from about 110° C. to about 150° C. 
     
     
       12. The process of  claim 10 , wherein the oxidation reaction temperature is controlled to be from about 110° C. to about 130° C. 
     
     
       13. The process of  claim 10 , wherein the oxidation reaction temperature starts at greater than or equal to about 130° C. and is reduced to about 100° C. after reaction initiation. 
     
     
       14. The process of  claim 1 , wherein the catalyst is Co(II) acetate and further comprising adding one of Mn(II) acetate, Ni(II) acetate, Zn(II) acetate, Zr(IV) acetate, Fe(II) acetate or combinations thereof as the additional metal acetate catalyst. 
     
     
       15. The process of  claim 1 , further comprising adding Co(III)(acetylacetonate) 3 , benzaldehyde, acetaldehyde or recycling intermediate methyl-biphenyl-aldehydes as an initiator. 
     
     
       16. The process of  claim 1 , wherein the catalyst concentration in the solution is from about 7.6 mM (450 ppm) to about 100 mM (6000 ppm). 
     
     
       17. The process of  claim 15 , wherein the catalyst concentration in the solution is from about 23 mM (1350 ppm) to about 100 mM (6000 ppm). 
     
     
       18. The process of  claim 1 , further comprising separation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products from under-oxidized intermediates and over-oxidized products, and recycling the under-oxidized intermediates to the oxidation process. 
     
     
       19. The process of  claim 1 , wherein the methyl-1,1′-biphenyl mono-carboxylic acids products formed are one or more of 3,3′-methyl-1,1′-biphenyl mono-carboxylic acid, 3,4′-methyl-1,1′-biphenyl mono-carboxylic acid, 4,3′-methyl-1,1′-biphenyl mono-carboxylic acid, and 4,4′-methyl-1,1′-biphenyl mono-carboxylic acid. 
     
     
       20. A process for forming methylbiphenyl mono-esters, comprising:
 providing a mixture of dimethylbiphenyl isomers; 
 separating 2,3′- and 2,4′-isomers of dimethylbiphenyl in the mixture from 3,3′-, 3,4′-, and 4,4′-isomers of dimethylbiphenyl by distillation, and then dissolving the 3,3′-, 3,4′- and 4,4′-isomers of dimethylbiphenyl in acetic acid to form a solution; 
 selectively oxidizing the dimethyl-1,1′-biphenyl(s) to form methyl-1,1′-biphenyl mono-carboxylic acid(s), by contacting the solution with an oxidation catalyst and air under time and temperature conditions sufficient to oxidize the dimethyl-1,1′-biphenyl(s) into one or more methyl-1,1′-biphenyl mono-carboxylic acid(s) products; 
 conducting at least one of: 
 (i) adding an antisolvent, or 
 (ii) optimizing a total conversion of dimethyl-1,1′-biphenyl(s) by oxidation based upon a molar ratio of dimethyl-1,1′-biphenyl isomers, or 
 (iii) precipitating the methyl-1,1′-biphenyl mono-carboxylic acid(s) products, or 
 (iv) optimizing the oxidation reaction temperature, 
 
       so as to limit over-oxidation of the dimethyl-1,1′-biphenyl(s);
 wherein the oxidation reaction is conducted in the absence of bromide-containing catalysts; and 
 wherein the total conversion is limited to 45-55% when the 3,3′-isomers of dimethylbiphenyl comprise between 10 and 30 wt % of the solution, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates; 
 further reacting the methyl-1,1′-biphenyl mono-carboxylic acid(s) products with C 4  to C 13  alcohols under esterification conditions. 
 
     
     
       21. The process of  claim 20 , wherein the catalyst is Mn(II) acetate or Co(II) acetate or combinations of Co(II) acetate and other metal acetate catalysts. 
     
     
       22. The process of  claim 20 , comprising adding water as the antisolvent. 
     
     
       23. The process of  claim 20 , further comprising limiting the total conversion to 55-70% when the 3,3′-isomers of dimethylbiphenyl comprise less than 10 wt % in the feed, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates. 
     
     
       24. The process of  claim 20 , further comprising limiting the total conversion to 30-45% when the 3,3′-isomers of dimethylbiphenyl comprise between 30 and 80 wt % in the feed, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates. 
     
     
       25. The process of  claim 20 , wherein precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products is achieved by removing solvent. 
     
     
       26. The process of  claim 20 , wherein precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products is achieved by optimizing the oxidation reaction temperature and solute concentrations of the methyl-1,1′-biphenyl mono-carboxylic acid(s), to cause precipitation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products prior to over-oxidation. 
     
     
       27. The process of  claim 26 , wherein the oxidation reaction temperature is reduced from an oxidation initiation temperature to from about 40° C. to less than about 60° C. 
     
     
       28. The process of  claim 26 , wherein the solute concentration of methyl-1,1′-biphenyl mono-carboxylic acid(s) products is above about 2 wt %. 
     
     
       29. The process of  claim 20 , wherein the oxidation reaction temperature is controlled to be from about 100° C. to about 150° C. 
     
     
       30. The process of  claim 29 , wherein the oxidation reaction temperature is controlled to be from about 110° C. to about 150° C. 
     
     
       31. The process of  claim 30 , wherein the oxidation reaction temperature is controlled to be from about 110° C. to about 130° C. 
     
     
       32. The process of  claim 29 , wherein the oxidation reaction temperature starts at greater than or equal to about 130° C. and is reduced to about 100° C. after reaction initiation. 
     
     
       33. The process of  claim 20 , wherein the catalyst is Co(II) acetate and further comprising adding one of Mn(II) acetate, Ni(II) acetate, Zn(II) acetate, Zr(IV) acetate, Fe(II) acetate or combinations thereof as the additional metal acetate catalyst. 
     
     
       34. The process of  claim 20 , further comprising adding Co(III)(acetylacetonate) 3 , benzaldehyde, acetaldehyde or biphenyl-aldehydes as an initiator. 
     
     
       35. The process of  claim 20 , wherein the catalyst concentration in the solution is from about 7.6 mM (450 ppm) to about 100 mM (6000 ppm). 
     
     
       36. The process of  claim 35 , wherein the catalyst concentration in the solution is from about 23 mM (1350 ppm) to about 100 mM (6000 ppm). 
     
     
       37. The process of  claim 20 , further comprising separation of the methyl-1,1′-biphenyl mono-carboxylic acid(s) products from under-oxidized intermediates and over-oxidized products, and recycling the under-oxidized intermediates to the oxidation process. 
     
     
       38. The process of  claim 20 , wherein the methyl-1,1′-biphenyl mono-carboxylic acids products formed are one or more of 3,3′-methyl-1,1′-biphenyl mono-carboxylic acid, 3,4′-methyl-1,1′-biphenyl mono-carboxylic acid, 4,3′-methyl-1,1′-biphenyl mono-carboxylic acid, and 4,4′-methyl-1,1′-biphenyl mono-carboxylic acid. 
     
     
       39. The process of  claim 20 , wherein the alcohols are OXO-alcohols. 
     
     
       40. A process for selective oxidation of dimethyl-1,1′-biphenyl(s) to form methyl-1,1′-biphenyl mono-carboxylic acid(s), comprising:
 providing a mixture of dimethylbiphenyl isomers; 
 separating 2,3′- and 2,4′-isomers of dimethylbiphenyl in the mixture from 3,3′-, 3,4′-, and 4,4′-isomers of dimethylbiphenyl by distillation, and then dissolving the 3,3′-, 3,4′- and 4,4′-isomers of dimethylbiphenyl in acetic acid to form a solution; 
 contacting the solution with an oxidation catalyst and air under time and temperature conditions sufficient to oxidize the dimethyl-1,1′-biphenyl(s) into one or more methyl-1,1′-biphenyl mono-carboxylic acid(s) products; 
 conducting at least one of: 
 (i) adding an antisolvent, or 
 (ii) optimizing a total conversion of dimethyl-1,1′-biphenyl(s) by oxidation based upon a molar ratio of dimethyl-1,1′-biphenyl isomers, or 
 (iii) precipitating the methyl-1,1′-biphenyl mono-carboxylic acid(s) products by lowering the temperature, or 
 (iv) decreasing the oxidation reaction temperature to enhance conversion of aldehydes over methyl functional groups, 
 
       so as to limit over-oxidation of the dimethyl-1,1′-biphenyl(s),
 wherein the oxidation reaction is conducted in the absence of bromide-containing catalysts, and 
 wherein the total conversion is limited to 30-45% when the 3,3′-isomers of dimethylbiphenyl comprise between 30 and 80 wt % of the solution, so as to increase the overall yield of methyl-1,1′-biphenyl mono-carboxylic acids relative to other 1,1′-biphenyl oxygenates.